Fuel delivery systems may include a direct fuel injector to inject fuel at high pressure directly into a cylinder. Highly pressurized fuel in the fuel delivery system may be particularly useful during crank and other times during engine operation for efficient combustion, etc. The direct fuel injector may deliver fuel in proportion to a fuel injector pulse width of a signal from an engine controller. However, due to aging, fuel contamination, or hardware failure, fuel injector may leak fuel unintentionally. Leaks in the fuel injector may cause the corresponding cylinder receiving fuel from the injector to misfire. Consequently, non-combusted air-fuel mixture may be displaced into the exhaust. The non-combusted air-fuel mixture in the exhaust may participate in an exothermic reaction at an exhaust catalyst generating excess amounts of heat. The heat generated may cause excessive increase in exhaust temperatures, which may result in thermal degradation of the exhaust components.
One example approach for mitigating fuel injector leak is shown by Wakemen et al. in U.S. Pat. No. 5,685,268. Therein, in response to detecting leakage in the fuel delivery system, the engine may be operated in a limp-home mode at reduced fuel pressure.
However, the inventors herein have identified potential issues with such an approach. As an example, build-up of deposits in the fuel injector can prevent the injector from closing completely, resulting in fuel leaking into the corresponding cylinder. Reducing the fuel rail pressure alone may not remove the deposits. As a result, the engine may be forced to shut down prematurely to prevent further leakage from the clogged injector until the clogged injector is replaced, or removed and cleaned.
In one example, the above issue may be addressed by a method, comprising: in response to diagnosing leak in a fuel injector, performing first high pressure mitigating actions for a first number of cylinder cycles, the first mitigating actions including increasing fuel rail pressure to a first rail pressure; and injecting fuel to all cylinders during compression stroke; and if the leak persists, reducing the rail pressure to a low rail pressure; and injecting fuel to all cylinders during intake stroke. In this way, by performing high pressure mitigating actions, blockage in the fuel injector that may prevent the injector from sealing may be reduced.
As an example, a fuel injector diagnostic test may identify leak in an injector (herein, also referred to as the leaking injector) delivering fuel to a cylinder. In response to diagnosing the leak, a controller may perform a first set of mitigating actions in order to blow out any potential deposits or blockage (accumulated due to contaminants in the fuel, aging, etc.) clogging the fuel injector and thus preventing the injector from sealing when fuel injection is not desired. The first set of mitigating actions may include increasing a fuel rail pressure (e.g., the rail pressure may be increased to a first pressure above a threshold pressure), increasing a pulse width delivered to the injector, and commanding fuel injection during compression stroke. Further, the first set of mitigating actions may be performed for a first number of cylinder cycles. In this way, by delivering increased amount of fuel during compression stroke at high pressure, deposits clogging the fuel injector may be blown-out.
Further, if the leak continues to persist after completion of the first set of mitigating actions, a second set of high pressure mitigating actions may be performed, which may include increasing the fuel rail pressure (e.g., the rail pressure may be increased to a second pressure above a threshold pressure), increasing the pulse width delivered to the injector, and commanding fuel injection to a cylinder receiving fuel from the leaking injector during intake stroke. In this way, suction generated by delivering increased amount of fuel at high pressure during intake stroke may be utilized to facilitate removal of the deposits clogging the injector when blowing out the injector by delivering fuel at high pressure during compression stroke did not result in stopping the leak. Still further, if the leak in the injector continues to persist, low pressure mitigating actions which include reducing the fuel rail pressure to a third pressure below the threshold pressure; and adjusting fuel injection timing to intake stroke injection may be utilized to reduce the leakage rate. However, after performing the second set of high pressure mitigating actions, if the leak is no longer detected, engine may resume normal operation based on the operating conditions.
In this way, by performing high pressure mitigating actions upon detecting leak in the fuel injector, deposits clogging the fuel injector may be reduced. As a result, an amount of fuel leaking out of the injector and into the cylinder may be reduced. Consequently, an amount of fuel available to participate in exothermic reactions at the catalytic converter may be reduced, thereby preventing excessive increase in exhaust temperatures and the resulting thermal degradation of the exhaust components. Further, during conditions when the high pressure mitigating actions result in reducing the leakage rate rather than complete stoppage of fuel leak, fuel penalty incurred until necessary repairs can be made may be reduced. Still further, by reducing the leakage rate the vehicle may not be disabled prematurely, and may continue to operate until necessary repairs can be made.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.